Re: [PATCH 2/9] KVM: x86: simplify read_emulated

Xiao Guangrong
2012-07-20T02:17:45Z

On 07/20/2012 07:58 AM, Marcelo Tosatti wrote:

>> - }
>> + rc = ctxt->ops->read_emulated(ctxt, addr, mc->data + mc->end, size,
>> + &ctxt->exception);
>> + if (rc != X86EMUL_CONTINUE)
>> + return rc;
>> +
>> + mc->end += size;
>> +
>> +read_cached:
>> + memcpy(dest, mc->data + mc->pos, size);
>
> What prevents read_emulated(size > 8) call, with
> mc->pos == (mc->end - 8) now?

Marcelo,

The splitting has been done in emulator_read_write_onepage:

while (bytes) {
unsigned now = min(bytes, 8U);

frag = &vcpu->mmio_fragments[vcpu->mmio_nr_fragments++];
frag->gpa = gpa;
frag->data = val;
frag->len = now;
frag->write_readonly_mem = (ret == -EPERM);

gpa += now;
val += now;
bytes -= now;
}

So i think it is safe to remove the splitting in read_emulated.